Modal verbs (and other verbs) to express Obligation

Modal verbs (and other verbs) to express OBLIGATION

Hello Everyone! Today we are looking at the verbs used to express obligation.

Must, should and ought to are the modal verbs used to express obligation. Ought to has exactly the same meaning as should but is not commonly used. Have to, which is a full verb, is also used to talk about obligation. Examples of statements, questions and negatives:-

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  1. Tom must help Kathy.
  2. Must Tom help Kathy?
  3. Tom mustnโ€™t help Kathy.
  1. Tom should help Kathy.
  2. Should Tom help Kathy?
  3. Tom shouldnโ€™t help Kathy.
  1. Tom has to help Kathy.
  2. Does Tom have to help Kathy?
  3. Tom doesnโ€™t have to help Kathy.

Must and have to are both used to talk about STRONG obligation.

Modal verbs (and other verbs) to express Obligation 2

Must is used when the speaker uses his/her authority and cares about the obligation being spoken about.

Example

Mother: โ€œEmma, you must do your homework!โ€ Emmaโ€™s mother is using her authority as Emmaโ€™s parent and wants her to do her homework. It is 100% important that Emma should do her homework.

Have to is used to express general obligation. The speaker has no authority over the person being spoken to.

Example

He must do his homework. (Present)
He had to do his homework. (Past)

He has to do his homework. (Present) He had to do his homework. (Past)

Mustnโ€™t and donโ€™t have to have completely different meanings in the negative.

Mustnโ€™t means forbidden and donโ€™t have to means no obligation but you can if you want to.

Example 1.
โ€œYou mustnโ€™t play with fire!โ€ You are forbidden from doing this โ€“ You could get burnt. You wouldnโ€™t say โ€œYou donโ€™t have to play with fireโ€ because that would mean that you can if you want to!

Example 2.
โ€œYou donโ€™t have to help me with the cookingโ€ There is no obligation but you can if you want to. (I may like some help). โ€œYou mustnโ€™t help me with the cookingโ€ means I forbid you from helping me. I really donโ€™t want your help!

The past of donโ€™t have to is didnโ€™t have to. It has exactly the same meaning as donโ€™t have to but in the past, i.e. there was no obligation but you could if you wanted to. E.g. When I was young I didnโ€™t have to help my mother with the cooking but, if I finished my homework early, I sometimes did.

The past of mustnโ€™t is wasnโ€™t allowed to which means was forbidden fromโ€ฆ E.g. โ€œWhen I was young I wasnโ€™t allowed to play with fireโ€ means โ€œWhen I was young I was forbidden from playing with fire.โ€

Should is used for mild obligation and advice.

Example

โ€œYou should do your homework.โ€ It is the right thing to do and I advise you to do it.

The negative of should is shouldnโ€™t as;

โ€œYou shouldnโ€™t go to bed too late.โ€ I advise you not to.

The past of should is should have. It means you didnโ€™t do something but it would have been the right thing to do.

Example

โ€œYou should have learned for the testโ€ โ€“ unfortunately, you didnโ€™t.

Shouldnโ€™t have means that you did something but it was the wrong thing to do.

Example
โ€œYou shouldnโ€™t have eaten all the pizzaโ€ โ€“ you did and it was the wrong thing to do!

To test your understanding of verbs of obligation, try grammar quiz as follows:

Grammar Quiz

Modal verbs (and other verbs) to express Obligation 3

See how much you understand about using verbs of obligation! Circle the correct sentence, A or B.

1.

A. Does he have to come to the meeting?

B. Has he to come to the meeting?

2.

A. You mustnโ€™t drink poison!

B. You donโ€™t have to drink poison!

3.

A. You donโ€™t have to come shopping with me but you can if you want to.

B. You mustnโ€™t come shopping with me but you can if you want to.

4.

A. Doctor โ€œYou have to take this medicine three times a day for a week.โ€

B. Doctor โ€œYou must take this medicine three times a day for a week.โ€

5.

A. Friend โ€œYou must pay your school fees!โ€

B. Friend โ€œYou have to pay your school fees!โ€

6.

A. When I was young I must help my mother clean our house.

B. When I was young I had to help my mother clean our house.

7.

A. Jim failed the exam! He should have studied harder!

B. Jim failed the exam! He had to study harder!

8.

A. Anna didnโ€™t has to buy me a present!

B. Anna didnโ€™t have to buy me a present!

9.

A. In India most school children must wear a uniform.

B. In India most school children have to wear a uniform.

10.

A. You mustnโ€™t drive over the speed limit!

B. You donโ€™t have to drive over the speed limit!

Answers: 1A, 2A, 3A, 4B, 5B, 6B, 7A, 8B, 9B, 10A

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